ViewTransitionTypeSet

Baseline 2026

Newly available

Since January 2026, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

The ViewTransitionTypeSet interface of the View Transition API is a set-like object representing the types of an active view transition. This enables the types to be queried or modified on-the-fly during a transition.

The ViewTransitionTypeSet object can be accessed via the ViewTransition.types property.

The property and method links below link to the JavaScript Set object documentation.

Instance properties

Set.prototype.size

Returns the number of values in the set.

Instance methods

Set.prototype.add

Inserts the specified value into this set, if it is not already present.

Set.prototype.clear()

Removes all values form the set.

Set.prototype.delete()

Removes the specified value from this set, if it is in the set.

Set.prototype.entries()

Returns a new iterator object that contains an array of [value, value] for each element in the set, in insertion order.

Set.prototype.forEach()

Calls a callback function once for each value present in the set, in insertion order.

Set.prototype.has()

Returns a boolean indicating whether the specified value exists in the set.

Set.prototype.keys()

An alias for Set.prototype.values().

Set.prototype.values()

Returns a new iterator object that yields the values for each element in the set, in insertion order.

Set.prototype[Symbol.iterator]()

Returns a new iterator object that yields the values for each element in the set, in insertion order.

Examples

js
// Start a view transition
const vt = document.startViewTransition({
  update: updateTheDOMSomehow,
  types: ["slideLeft", "fadeOut", "flipVertical"],
});

// Add another type
vt.types.add("flipHorizontal");

// Delete a type
vt.types.delete("flipVertical");

// Return the number of types in the set
console.log(vt.types.size);

// Log each type to the console
vt.types.forEach((type) => console.log(type));